Coating processes – Nonuniform coating – Edge or border coating
Reexamination Certificate
1998-07-06
2001-07-31
Parker, Fred J. (Department: 1762)
Coating processes
Nonuniform coating
Edge or border coating
C427S289000, C427S300000
Reexamination Certificate
active
06268020
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to gasket sheets which have good sealing properties even at low flange pressures. More particularly, the present invention provides a gasket which can be used to seal fluids. Gaskets of the present invention, placed in a flange and having to seal against fluids, can seal against fluid leaks both going through the gasket sheet internally and across the gasket face.
Gasket sheets are used to seal fluids in engines. A number of solutions have been employed in order to obtain good sealability (sealing ability) in the gaskets.
Beading on the face of the gasket is known. Such beading is a raised area put on the face; this beading, however, does not extend past the edge and further does not extend onto the edge. Such beading is used to enhance sealing.
One gasket material which can be used to give a good seal at high temperatures is described in U.S. Pat. No. 5,240,766. This reference describes a gasket sheet material having fiber, filler, and binder. According to the reference, the filler component provides desirable sealability.
Another reference which describes gasket sheet materials is U.S. Pat. No. 5,536,565. This reference describes a gasket sheet material with fiber and filler. The filler component must include a gel-forming mineral. This filler gives the gasket good sealing properties, especially against polar liquids.
In spite of the wide use of gaskets to obtain a seal against fluids in engines, obtaining a good seal continues to be a problem in gasket sheet materials. Many gaskets do not seal well at low flange pressures. Other gaskets are given particular coatings in order to obtain a gasket sheet which will seal well. Unfortunately, such coatings are then responsible for the gasket having poor compression failure resistance.
The gaskets described herein provide good sealing ability even at low flange pressures. In some embodiments the gasket is not coated or has only a limited amount of a coating given in order to obtain good sealability, thus allowing the gasket to also be compression failure resistant.
SUMMARY OF THE INVENTION
A gasket sheet comprising two opposed faces, and an aperture with a gasket sheet edge (also called the aperture's edge or the aperture's gasket sheet edge) which is substantially perpendicular to the opposed faces. The sheet edge further has at least one body which forms a barrier or dam to retard fluid from going from the aperture, past the edge and across a face of the gasket. The barrier can protrude from the edge or from the gasket face. When the barrier protrudes from the edge it gets wider in a direction perpendicular to a facial plane of the gasket, and it protrudes past a corner plane at some point between the sheet edge and the aperture. The barrier is sufficiently wide to retard the flow of fluid from the aperture across the face of the gasket, thus the barrier protrudes a sufficient distance past the corner of the gasket sheet edge to be effective to give the gasket a better sealing ability than the gasket would have if the barrier stopped at a point in a plane going through the corner of the edge (stopped at the corner between the face and the edge).
In most embodiments of this invention the barrier is formed by a coating that is wider than the thickness of the aperture's gasket sheet edge, measuring the width of the coating going in a direction parallel to the sheet edge from one of the corners between the edge and the face through the other corner between the edge and the other face. The coating, at the edge, thus being sufficiently wide to protrude past at least one of said corners in a direction parallel to the surface of the sheet edge. The coating on the edge of the gasket sheet at the aperture goes beyond one of said corners in an amount sufficient to give the gasket a better sealing ability than the gasket would have if the coating was only as wide as the thickness of the gasket sheet edge and thus stopped at both corners. The coating, however, does not necessarily lap around the corner onto the face of the gasket, although optionally, it can.
The coating on the sheet edge, going beyond at least one of the corners laying between a face and the aperture's gasket sheet edge (where the edge meets a gasket face), is herein referred to as a “wide edge coating” or a “protruding coating”. The corner is located at each side of the edge where it abuts the face, at the point between the face and the edge; this point can be identified easily as the point where the cut, frequently porous edge ends and the less porous, non-cut face of the gasket begins.
In some embodiments the gasket is given a protruding coating on the sheet edge which is around the outside of the gasket (coating C). This is a secondary sealing position which seals the fluid from leaking past the gasket and outside of the flange, and as such it is less preferred than the coatings on the aperture's edge which seals the gasket where the gasket is first and primarily exposed to fluid (giving a primary seal). The edge coating around the perimeter of the gasket (coating C), must protrude past at least one corner of the edge of the gasket sheet, and preferably, in embodiments where the facial plane does not go through the corner of the gasket edge, the coating protrudes past the facial plane.
The protruding coating, given to the gasket, may extend onto either or both faces, and may extend so far as to completely cover one or both faces of the gasket except that the coating must protrude to provide the barrier, and not be a level coating over the gasket. When the edge coating sticks up past the corner plane or facial plane at an edge, the coating provides a dam to retard fluids from going from the aperture past the edge and out onto the gasket face between the face and a flange; where the edge is a perimeter edge the coating protrusion will stop fluids from going past the gasket out of the flange.
Furthermore, a completely coated gasket can take advantage of the sealing ability provided by the instant invention, although in some embodiments, to preserve compression failure resistance the amount of coating is preferably limited to cover only a portion of the gasket, the rest of the gasket being left uncoated. In such embodiments it is preferred to use a wide edge-coating to seal off the aperture's gasket sheet edge to fluids that go through the gasket itself. Preferably, to preserve compression failure resistance a coating will cover up to about 50% of the gasket, and even more preferably it is limited to cover a maximum of about 30% of the gasket. In another preferred embodiment there is no coating on either face of the gasket so that the gasket has optimized compression failure resistance.
Compression failure resistance is the ability of a gasket structure to withstand pressure without deforming the gasket to the point of failure. The crush test is an industry accepted measurement of compression failure resistance. The degree of compression failure resistance that a gasket must have is typically set by the load that it will experience in a particular application or in a specific flange.
Suitably, the coating on the edge covers all of the portions of the edge which must be coated in order to give the gasket a good sealing ability. It may not be necessary, for example, to have the coating on the edge at bolt areas, or at non-porous portions of the edge. The edge is coated to allow the gasket to provide a better seal. Acceptable embodiments include instances where the coating covers major portions of the edge. The gasket sheet edge can, thus be coated in an effective amount to achieve a substantial sealing of the gasket along the edge of the aperture. The edge, for example, can be coated up to about 75% of the aperture's gasket edge. Such embodiments can be used for good sealing ability, where the very best sealing ability, obtained from coating the entire edge of the gasket does not have to be used. Preferably, however, the entire edge of the aperture is coated.
REFEREN
Dempsey Dennis M.
Forry John S.
Lehr Brian C.
Morris Christopher L.
Sload Linda L.
Interface Solutions, Inc.
Parker Fred J.
Womble Carlyle Sandridge & Rice PLLC
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